Tommy Kwong-Kin Tsang

Ultra-wideband (UWB) communications systems: an overview

This paper presents an overview of the ultra-wideband (UWB) technology for wireless communications systems. Following a brief review of the UWB basic principles, the characteristics of application specific UWB wireless systems are described. Design principles and challenges of UWB wireless systems, with an emphasis on monolithic implementations are discussed. Trade-offs between performance, power consumption, and technology choices are addressed. Examples of state-of-the-art UWB circuits and systems are presented.

Distortion in RF CMOS short-channel low-noise amplifiers

An approach to estimate the distortion in CMOS short-channel (e.g. 0.18-/spl mu/m gate length) RF low-noise amplifiers (LNAs), based on Volterras series, is presented. Compact and accurate frequency-dependent closed-form expressions describing the effects of the different transistor parameters on harmonic distortion are derived. For the first time, the second-order distortion (HD2), in CMOS short-channel based LNAs, is studied. This is crucial for systems such as homodyne receivers. Equations describing third-order intermodulation distortion in RF LNAs are reported. The analytical analysis is verified through simulations and measured results of an 0.18-/spl mu/m CMOS 5.8-GHz folded-cascode LNA prototype chip geared toward sub-1-V operation. It is shown that the distortion is independent of the gate-source capacitance C/sub gs/ of the MOS transistors, allowing an extra degree of freedom in the design of LNA circuits. Distortion-aware design guidelines for RF CMOS LNAs are provided throughout the paper.

Gain and frequency controllable sub-1 V 5.8 GHz CMOS LNA

This paper presents the design and experimental results of a low-voltage low noise amplifier (LNA) with gain and frequency control in a standard 0.18 /spl mu/m CMOS process. Targeting at a center frequency of 5.8 GHz with a supply voltage of 1 V, the LNA exhibits a power gain of 13.2 dB with a noise figure of 2.5 dB. The circuit has over 10 dB of gain tuning, and 360 MHz of frequency tuning, and can operate at a supply voltage as low as 0.7 V.

Recent advances and future trends in low power wireless systems for medical applications

This paper describes current state-of-the-art research on low power wireless systems for medical applications. Distinct design criteria and challenges in this area are addressed. A study of existing wireless technologies and their key applications are presented. A brief assessment of future trends for wireless medicine with a focus on emerging technologies is provided. Finally, a number of different energy-scavenging techniques for the future development of autonomous wireless nodes are reviewed.

Design Techniques of CMOS Ultra-Wide-Band Amplifiers for Multistandard Communications

This paper presents design techniques of CMOS ultra-wide-band (UWB) amplifiers for multistandard communications. The goal of this paper is to propose a compact, simple, and robust topology for UWB low-noise amplifiers, which yet consumes a relatively low power. To achieve this goal, a common-gate amplifier topology with a local feedback is employed. The first amplifier uses a simple inductive peaking technique for bandwidth extension, while the second design utilizes a two-stage approach with an added gain control feature. Both amplifiers achieve a flat bandwidth of more than 6 GHz and a gain of higher than 10 dB with supply voltages of 1.8-2.5 V. Designs with different metal thicknesses are compared. The advantage of using thick-metal inductors in UWB applications depends on the chosen topology.

Dual-band sub-1 V CMOS LNA for 802.11a/b WLAN applications

This paper presents the design and experimental results of a dual-band CMOS low noise amplifier (LNA), which can operate from a supply voltage as low as 0.7 V. A switched inductor technique is used. The LNA was fabricated in a standard 0.18 /spl mu/m CMOS process, and is designed to be used in a dual-band 2.4- and 5-GHz WLAN receiver. With a 1 V supply, the LNA exhibits a measured power gain and noise figure of S/sub 21/=11.6 dB and NF=2.3 dB for the 2.4 GHz band, and S/sub 21/=10.8 dB and NF=2.9 dB for the 5 GHz band.

Radio-triggered solar and RF power scavenging and management for ultra low power wireless medical applications

The design of a dual-source power scavenging and management system for ultra low power wireless medical applications is presented. Power scavenging is achieved by harvesting energy both from solar (primary) and RF power (secondary) sources. Depending on the available energy, the system can supply 1-2mW of power to a wireless device, with up to a 50% duty cycle. A radio-triggering based technique is used to control the activation and shutting down of the complete wireless system, and thus eliminates energy wasting wake-up periods. The system provides a regulated output voltage of 1.5V, with a total power consumption of less than 8.0muW in the sleep mode, and 48muW in the operating mode

Distortion in RF CMOS short channel low noise amplifiers

An approach to estimate the distortion in CMOS short-channel (0.18 /spl mu/m gate length) RF low noise amplifiers (LNA), based on Volterras series, is presented. Compact and accurate frequency-dependent closed form expressions describing the effects of the different transistor parameters on harmonic distortion are derived. For the first time, the second order distortion (HD2), which is crucial in homodyne receivers, is studied. The analytical analysis is verified through simulations and measured results of a 0.18 /spl mu/m CMOS 5.8GHz folded-cascode LNA prototype chip geared towards sub-IV operation. Distortion-aware design guidelines for RF CMOS LNAs are provided throughout the paper.

Very wide tuning range micro-electromechanical capacitors in the MUMPs process for RF applications

A structure that extends the tuning range of MEMS capacitors by at least a factor of eight, compared to recently reported devices fabricated in the same polysilicon surface micromachining MUMPs process, is proposed. A 0.2 pF capacitor has a 325% tuning range, and a Q-factor of 90 at 2.4 GHz. A variation of the same structure has a 0.6 pF capacitance and a 433% tuning range, compared to 238% and 253% for state-of-the-art MEMS and CMOS devices, respectively. The self-resonance frequencies of both devices are beyond 4 GHz.

A fully integrated 1 V 5.8 GHz bipolar LNA

This paper describes a low voltage low noise amplifier design in a 0.5 /spl mu/m bipolar process, targeting a center frequency of 5.8 GHz with a voltage supply of 1 V. The forward transmission S/sub 21/ is 11.5 dB at a low power consumption of 6.6 mW, including all biasing circuitry. The overall noise figure of the LNA is 4 dB with both input and output impedances matched to 50 ohm. The circuit uses no off-chip components, such as bonding wires and biasing-tees, which makes it suitable for robust integration.